The present invention relates to turbochargers for use in internal combustion engines, and, more particularly, to a turbocharger having two or more compressor stages driven by one turbine.
A limiting factor in the performance of an internal combustion engine is the amount of combustion air that can be delivered to the intake manifold for combustion in the engine cylinders. Atmospheric pressure is often inadequate to supply the required amount of air for proper operation of an engine.
An internal combustion engine, therefore, may include one or more turbochargers for compressing air to be supplied to one or more combustion chambers within corresponding combustion cylinders. The turbocharger supplies combustion air at a higher pressure and higher density than existing atmospheric pressure and ambient density. The use of a turbocharger can compensate for lack of power due to altitude, or to increase the power that can be obtained from an engine of a given displacement, thereby reducing the cost, weight and size of an engine required for a given power output.
Each turbocharger typically includes a turbine driven by exhaust gases from the engine, and a compressor driven by the turbine. The compressor receives the air to be compressed and supplies the air to the combustion chamber. It is known to drive the compressor via a shaft carrying both the compressor wheel and the turbine wheel.
It is known to provide higher compression levels through the use of a multi-stage turbocharger. A known multi-stage turbocharger includes a turbine section and two or more compressor sections. A common shaft interconnects the turbine wheel of the turbine section with compressor wheels in the compressor sections. A stream of exhaust gases from the engine is conducted from the exhaust manifold to the turbine section of the turbocharger The stream of exhaust gases passing through the turbine section causes the turbine wheel to rotate, thereby turning the common shaft interconnecting the turbine wheel and the compressor wheels and rotating the compressor wheels.
Ambient air to be used for combustion in the internal combustion engine is brought into an inlet for the first compressor section. The air is compressed by the first compressor wheel, and passes from the first compressor section through a first compressor section outlet to the inlet of the second compressor section, for further compression. An interstage duct is used to conduct the compressed air from the first compressor section outlet to the inlet of the second compressor section. The out flow from the second compressor section exits the turbocharger at the second compressor section outlet, and is directed to the inlet manifold of the internal combustion engine.
U.S. Pat. No. 4,344,289 (Curiel et al.) discloses a supercharger with a two-stage compressor having two compressor wheels which are disposed in a back-to-back orientation relative to each other and carried by a common shaft. It is also known to provide two compressors operating to separately compress volumes of air supplied to a common duct. U.S. Pat. No. 5,157,924 (Sudmanns) discloses compressor wheels disposed in a face-to-face manner relative to each other, and which are carried by a common shaft.
Several problems are experienced with previously known constructions for turbochargers as described above. Providing a common shaft carrying the turbine wheel and two or more compressor wheels for separate compressor stages results in an undesirably large structure, difficult to arrange in an engine compartment. The combined mass of the turbine wheel and compressor wheels, even though positioned at different locations along the shaft, can cause shaft deflections. It is difficult to mount bearings accurately, and premature wear can be a problem. Further, since the compressor wheels are mounted directly on a single shaft, it has not been possible to optimize all compressor wheel speeds for optimum turbocharger performance.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the invention, a turbocharger for an internal combustion engine is provided with a turbine including a turbine shaft, a turbine wheel carried by the turbine shaft, and a drive gear carried by the turbine shaft. A compressor includes a compressor shaft, a compressor wheel carried by the compressor shaft, and a driven gear carried by the compressor shaft. The driven gear is operatively engaged with the drive gear.
In another aspect of the invention, an internal combustion engine is provided with a plurality of combustion cylinders, an intake manifold fluidly coupled for supplying combustion gas to the plurality of combustion cylinders, and an exhaust manifold fluidly coupled to receive a flow of exhaust gases from the plurality of combustion cylinders. A turbocharger includes a turbine having a rotatable turbine shaft, a turbine wheel carried by the turbine shaft, a drive gear carried by the turbine shaft and a turbine inlet and a turbine outlet associated with the turbine wheel. The turbine inlet is connected in flow communication with the exhaust manifold. A first compressor includes a first compressor shaft, a first compressor wheel carried by the first compressor shaft, a first driven gear carried by the first compressor shaft, and a first compressor inlet and a first compressor outlet associated with the first compressor wheel. The first driven gear is operatively engaged with the drive gear, and the first compressor outlet is connected in flow communication with the intake manifold.
In yet another aspect of the invention, a method of operating a turbocharger in an internal combustion engine is provided, with the steps of providing a turbine including a turbine shaft, a turbine wheel carried by the turbine shaft, and an inlet and an outlet associated with the turbine wheel; providing a first compressor including a first compressor shaft, a first compressor wheel carried by the first compressor shaft, and a first compressor inlet and a first compressor outlet associated with the first compressor wheel; providing driving engagement of the first compressor shaft with turbine shaft; circulating a fluid stream to the turbine inlet and through the turbine to the turbine outlet, and rotating the turbine wheel and the turbine shaft thereby; and rotating the first compressor shaft and the first compressor wheel through the driving engagement of the first compressor shaft and the turbine shaft.